1. Lecture 8 Titrations - II

2. Kjeldahl digestion Conc. H 2 SO 4 + catalyst All N  NH 4 + C  CO 2 HH2OHH2O >300 o C

3. NaOH+NH 3 NH 3 +H 2 O HCl or H 3 BO 3 NH 3 + H +  NH 4 + Excess of H + can be titrated with NaOH If HCl: If boric acid: B(OH) 4 - + H +  H 3 BO 3 + H 2 O

4. Precipitation Titration AgNO 3 + NaCl  AgCl + NaNO 3 Ag + + Cl -  AgCl

5. AgCl  Ag + + Cl - K SP = [Ag + ][Cl - ] pX = - log 10 [X] pAg = - log 10 [Ag + ]

6. n- soluble AgCl Cl - Na + AgNO 3 NO 3 - AgCl Na + NO 3 - AgNO 3 Colloid equivalence point: coagulation no chloride ion left in solution, no further precipitation possible @ first drops In the middle

7. Equivalence point [Ag + ]=[Cl - ] 100.1% Ag + 99.9% Ag + [Cl - ]=10 -4 M  [Ag + ]=1.8  10 -6 M [Ag + ]=10 -4 M Acceptable end point Titration of NaCl with AgNO 3 C=0.1 M

8. I - + Ag +  AgI pAg= -log[Ag + ] K sp (AgI)=[Ag + ][I - ]=8.3  10 -17 99.9% Ag + 100.1% Ag + Acceptable end point

10. Precipitation titration with silver electrode The change of V is proportional to pAg V(mV)

12. Ag + + + + + + + + + + Ind 2- Ag + I-I- I-I- I-I- I-I- _ _ _ _ _ _ _ _ Ind 2-

13. Precipitation Titrations: